1. Field of the Invention
The present invention relates to a head suspension for a disk drive incorporated in an information processing apparatus such as a personal computer.
2. Description of the Related Art
A hard disk drive (HDD) records and reproduces information to and from rotating magnetic or magneto-optical disks. The HDD has a carriage that is turned around a spindle by a positioning motor.
An example of the carriage is disclosed in U.S. Pat. No. 4,167,765. The carriage of this disclosure includes carriage arms, a head suspension attached to a front end of each carriage arm, a head attached to the head suspension, and a slider attached to the head. The sliders face disks. When the disks are rotated at high speed, the sliders slightly float from the disks, and air bearings are formed between the disks and the sliders.
The head suspension includes a load beam made of a precision thin plate spring, a flexure made of a very thin plate spring fixed to a front part of the load beam by, for example, laser welding, and a plate fixed to a base of the load beam by, for example, laser welding. The plate is fixed to a head suspension fitting face of the carriage arm.
Recent hard disk drives employ high-density disks and drive the disks at high speed. For such high-density disks, the head suspensions must have excellent vibration characteristics to correctly position the heads on narrow tracks of the disks and characteristics to avoid the influence of air disturbance caused by the disks rotating at high speed. To include such and other requirements, the head suspensions are frequently subjected to intricate processes.
The high-density disks require head suspensions having high rigidity and low spring constants. To meet the requirement, the present inventor proposed in Japanese Patent Laid Open Publication No. 2001-155458 a head suspension 101 of FIG. 12, which differs from a conventional head suspension having a load beam composed of an integrated rigid part and resilient part.
In FIG. 12, the head suspension 101 has a plate 103, a load beam 105, and a flexure 107.
The plate 103 is attached to a carriage arm of a carriage. The carriage drives the head suspension 101 around a spindle.
The load beam 105 applies load on a slider 108 arranged at a front end of the load beam 105. The load beam 105 consists of a rigid part 109 and a resilient part 111. The resilient part 111 is made of a resilient material 113 that is independent of the rigid part 109.
The resilient material 113 is a rectangular plate and has an opening 115 to form the resilient part 111. A first side 113a of the resilient material 113 is laid on an end 109a of the rigid part 109 and is fixed thereto by, for example, laser welding or bonding. A second side 113b of the resilient material 113 is laid on an end 103a of the plate 103 and is fixed thereto by, for example, laser welding or bonding.
The flexure 107 is attached to the rigid part 109 of the load beam 105 by, for example, laser welding and is extended over the resilient material 113 toward the plate 103. Referring also to FIG. 13, which is a longitudinal section partly showing the head suspension 101, the flexure 107 consists of a metal base 117 made of, for example, a resilient thin stainless steel rolled plate, an electric insulating layer 118 formed on the metal base 117, and a conductive path 119 formed in the insulating layer 118. An end of the conductive path 119 is electrically connected to a terminal of the head 121, and the other end of the conductive path 119 is electrically connected to a terminal 123 for external connection.
In the head suspension 101, the load beam 105 consists of the rigid part 109 and resilient material 113 that are separate from each other. Namely, the rigid part 109 and resilient material 113 may be made of proper materials of their own and may have proper thicknesses of their own, to easily and simultaneously realize required properties such as high rigidity for the rigid part 109 and a low spring constant for the resilient part 111. The resilient part 111 may be made of a precision rolled plate, to provide a stable low spring constant.
The separate rigid part 109 and resilient material 113, however, form an overlapping part 125 between them. Where the flexure 107 is on the overlapping part 125, the impedance of the conductive path 119 is affected.
In FIG. 13, the metal base 117 of the flexure 107 is provided with an oblong slot 127. The slot 127 is made by partly removing the metal base 117 under the conductive path 119, to improve electric characteristics. Namely, the slot 127 reduces electric capacitance between the conductive path 119 and the metal base 117, to increase an electric resonance frequency. The slot 127 also functions to realize electric alignment with respect to flexible cables or ICs connected to the head 121 or head suspension 101, thereby correctly transmitting signals.
Under the slot 127, there is another metal layer such as the rigid part 109, which also produces electric capacitance. If the distance between the flexure 107 and the rigid part 109 changes, electric capacitance between them also changes, to vary electric characteristics and spoil the function of the slot 127.
If the rigid part 109 and resilient part 111 are integral with each other, there will be no overlapping part 125 between them, and therefore, the flexure 107 will closely be attached to the load beam 105 and will maintain, even with the presence of the slot 127, constant electric capacitance from the rigid part 109 to the resilient part 111. However, the flexure 107 of FIG. 13 crosses the overlapping part 125. Namely, the flexure 107 changes its state from FIG. 14, which is a sectional view taken along a line SE—SE of FIG. 13, to FIG. 15, which is a sectional view taken along a line SF—SF of FIG. 13. In FIG. 15, the flexure 107 forms a gap 129 with respect to a surface 109b of the rigid part 109. Between the state of FIG. 14 in which the flexure 117 is tightly attached to the surface 109b and the state of FIG. 15 in which the flexure 117 forms the gap 129, the flexure 117 changes its electric capacitance to vary the impedance of the conductive path 119.
Signals transmitted through the conductive path 119 are weak, and therefore, such impedance variations hinder precision write and read operations.
The flexure 107 extended across the overlapping part 125 not only forms the gap 129 with respect to the rigid part 109 but also protrudes from the overlapping part 125 to disturb airflow to flutter the flexure 107 and load beam 105 when disks in the disk drive are rotated at high speed.